Immunoassays utilize the specific binding capabilities of antibodies to detect the presence of target molecules in solution. Although the general principle is applicable to a broad range of problems, major commercial interest has centered on medical diagnostic applications for a wide variety of analytes in biological fluids such as blood, saliva, and urine.
Several types of immunoassays, useful for distinct applications, already exist. Each such assay type requires a way of distinguishing whether binding sites on an antibody are occupied or free. Typically this is accomplished by means of label such as an atom, molecule, enzyme or particle attached permanently to either the antibody or to an analog of the analyte.
There is a need for quick, accurate, simple assays that can be performed by laboratory personnel as well as by non-technical personnel outside of a laboratory setting. Such assays are necessary as society becomes increasingly concerned about the use of drugs, tobacco and alcohol. For example, in the workplace, testing for drug use is becoming more common. Insurance companies also need to establish whether a client uses tobacco or illicit drugs to calculate risk and establish insurability. Police officers in the field frequently administer tests for alcohol use; simple tests for use of illicit or impairing drugs would similarly aid law enforcement.
It is an object of the present invention to provide an assay method and a device for performing the assay that allows detection of an analyte in a sample under either laboratory or field conditions.